System and method for controlling flow through a rotor

ABSTRACT

One embodiment of the present invention is a system for controlling flow through a rotor. The system includes an inlet port in the rotor and an outlet port in the rotor. The outlet port is in fluid communication with the inlet port. A fixed orifice is disposed in at least one of the inlet or outlet ports. A variable orifice is disposed in at least one of the inlet or outlet ports in a separate location from the fixed orifice.

FIELD OF THE INVENTION

The present invention generally involves a system and method for controlling flow through a rotor. For example, particular embodiments of the present invention may control the amount of fluid diverted through a rotor to warm up the rotor.

BACKGROUND OF THE INVENTION

Gas turbines are widely used in industrial and commercial operations. A typical gas turbine includes a compressor at the front, one or more combustors around the middle, and a turbine at the rear. The compressor imparts kinetic energy to the working fluid (e.g., air) to produce a compressed working fluid at a highly energized state. The compressed working fluid exits the compressor and flows to the combustors where it mixes with fuel and ignites to generate combustion gases having a high temperature and pressure. The combustion gases flow to the turbine where they expand to produce work. For example, expansion of the combustion gases in the turbine may rotate a shaft connected to a generator to produce electricity.

The compressor and the turbine typically share a common rotor which extends from near the front of the compressor, through the combustor section, to near the rear of the turbine. Due to the length and size of the rotor, the total weight of the rotor may approach or exceed 100 tons. During startup of the gas turbine, as compressed working fluid flows through the compressor and combustion gases flow through the turbine, the outer portion of the rotor heats up faster than the inner portion of the rotor creating a temperature gradient across the rotor profile. The temperature gradient across the rotor profile produces substantial thermal stresses across the rotor that are generally proportional to T_(max)−T_(ave). T_(max) is the maximum temperature across the rotor profile. In compressor section, T_(max) may approach the temperature of the compressed working fluid exiting the compressor, and in the turbine section, T_(max) may approach the temperature of the combustion gases entering the turbine. T_(ave) is the average temperature across the rotor profile and is initially ambient temperature during a cold startup of the gas turbine. The thermal stress across the rotor continues until the temperature across the rotor profile reaches equilibrium, which may be 12 hours or longer, and substantially reduces the low cycle fatigue limit of the rotor.

Various systems and methods are known in the art for reducing the thermal stress across the rotor. For example, a process fluid may be diverted from the compressor to flow through the rotor to decrease the differential temperature between T_(max) and T_(aw) and allow the rotor to reach equilibrium temperature in a shorter period of time. However, the diverted fluid decreases the efficiency of the compressor by reducing the amount of compressed working fluid produced by the compressor. In addition, the diverted fluid creates turbulence as it is reintroduced into the compressor airflow, and the turbulence may create laminar separation across the compressor blades. Therefore, an improved system and method for controlling flow through a rotor would be useful.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention are set forth below in the following description, or may be obvious from the description, or may be learned through practice of the invention.

One embodiment of the present invention is a system for controlling flow through a rotor. The system includes an inlet port in the rotor and an outlet port in the rotor. The outlet port is in fluid communication with the inlet port. A fixed orifice is disposed in at least one of the inlet or outlet ports. A variable orifice is disposed in at least one of the inlet or outlet ports in a separate location from the fixed orifice.

Another embodiment of the present invention is a system for warming a rotor. The system includes a fluid passage through the rotor. A first valve is disposed in the fluid passage to control the flow of a fluid through the fluid passage. A second valve is disposed in a different location in the fluid passage from the first valve to control the flow of a fluid through the fluid passage.

The present invention may also include any method for controlling flow through a rotor. The method includes diverting a process fluid and flowing the diverted process fluid through a fluid passage in the rotor, the fluid passage including a first orifice and a second orifice that is separate from the first orifice. The method further includes reducing the flow of be diverted process fluid through the fluid passage in the rotor by using the first orifice, second orifice, or combinations thereof.

Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the specification.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:

FIG. 1 is a simplified cross-section view of a rotor according to one embodiment of the present invention;

FIG. 2 is a perspective view of one side of a rotor wheel shown in FIG. 1 taken along line A-A; and

FIG. 3 is a perspective view of another side of a rotor wheel shown in FIG. 1 taken along line B-B.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention.

Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features illustrated or described as part of one embodiment may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

Embodiments within the scope of the present invention provide a system and method for enhancing the expected life of a rotor and improving the efficiency of a gas turbine. In various embodiments, the present invention may control the flow of a fluid through the rotor to warm the rotor, thereby reducing thermal stresses across the rotor profile. The reduced thermal stresses will enhance the low cycle fatigue limits of the rotor. In addition, embodiments within the scope of the present invention enhance the gas turbine efficiency by controlling the amount and/or duration of fluid flow through the rotor. In this regard, it has been determined that dual metering can be utilized to provide a fixed metering area which controls fluid flow until a full load condition when a second, separate active metering area can be utilized to reduce flow.

FIG. 1 provides a simplified cross-section view of the top half of a rotor 10 according to one embodiment of the present invention. As shown, the rotor 10 may comprise a plurality of rotor wheels 12 axially connected by a tie rod 14 to rotate together around a centerline 16. In the compressor section, each rotor wheel 12 may be associated with a rotating blade 18 or stationary nozzle 20, as shown in FIG. 1. Similarly, in the turbine section, each rotor wheel 12 may be associated with a rotating bucket or stator.

As shown in FIG. 1, the rotor 10 includes a plurality of cavities 22 between and through adjacent rotor wheels 12. The cavities 22 reduce the total weight of the rotor 10. In addition, the cavities 22 provide one or more fluid passages between and around adjacent rotor wheels 12. The fluid passages include at least one inlet port 24 and at least one outlet port 26 in fluid communication with the inlet port 24. The inlet and/or outlet ports 24, 26 may comprise any suitable passage, plenum, or pathway through a single rotor wheel 12 or between adjacent rotor wheels 12. For example, as shown in FIG. 2, the inlet port 24 or outlet port 26 may comprise a radial bore hole between adjacent rotor wheels 12. In this manner, a fluid may flow through the inlet port 24 into the fluid passage and through and/or around the rotor wheels 12 before exiting the fluid passage through the outlet port 26, as indicated by the flow arrows in FIG. 1.

A variable orifice 28 may be disposed in the fluid passage in at least one of the inlet or outlet ports 24, 26 to control the fluid flow through the fluid passage. For example, the variable orifice 28 may have a first position that permits fluid flow through at least one of the inlet or outlet ports 24, 26 and a second position that reduces and/or prevents fluid flow through at least one of the inlet or outlet ports 24, 26. The variable orifice 28 may comprise any suitable mechanism known to one of ordinary skill in the art for preventing or preventing fluid flow. For example, as shown in FIG. 3, the variable orifice 28 may comprise a thermally actuated valve 30 that responds to temperature changes in the rotor wheels 12. As shown in FIG. 3, the valve 30 may include a piston 32 or disk connected to a diaphragm 34 inside the valve 30. At lower temperatures, the diaphragm 34 may contract to retract the piston 32 or disc into the valve 30 to place the variable orifice 28 in the first position that allows or permits fluid flow through at least one of the inlet or outlet ports 24, 26. As the rotor wheel 12, and thus the rotor 10, increases temperature, the diaphragm 34 may expand to force the piston 32 or disk out of the valve 30 to obstruct or completely seal off the associated inlet or outlet port 24, 26. With the piston 32 or disk extended into the associated inlet or outlet port 24, 26, the variable orifice 28 is in the second position which reduces or prevents fluid flow through at least one of the inlet or outlet ports 24, 26.

A fixed orifice 40, which is separate from the variable orifice 28, may also be disposed in the fluid passage in at least one of the inlet or outlet ports 24, 26 to control the fluid flow through the fluid passage. For example, the fixed orifice 40 may have a first position that permits fluid flow through at least one of the inlet or outlet ports 24, 26 and a second position that reduces and/or prevents fluid flow through at least one of the inlet or outlet ports 24, 26. The fixed orifice 40 can initially control fluid flow until a full load condition. In this manner, fixed orifice 40 in conjunction with variable orifice 28 can more reliably control purge flows. Similar to the variable orifice 28, fixed orifice 40 can comprise any suitable mechanism known to one of ordinary skill in the art for preventing or preventing fluid flow.

As shown in FIG. 1, the variable orifice 28 and fixed orifice 40 may be connected to a controller 36 for remote operation of the variable orifice 28 in alternate embodiments within the scope of the present invention. Although not illustrated, variable orifice 28 and fixed orifice 40 can be controlled by separate controllers as well as would be understood by one of ordinary skill in the art. As described herein, the technical effect of the controller 36 is to transmit a signal 38 to the variable orifice 28 and/or fixed orifice 40 to remotely operate such orifice(s). The controller 36 may be a stand alone component, such as a temperature sensor or timer, or a sub-component included in any computer system known in the art, such as a laptop, a personal computer, a mini computer, or a mainframe computer. The various controller and computer systems discussed herein are not limited to any particular hardware architecture or configuration. Embodiments of the systems and methods set forth herein may be implemented by one or more general-purpose or customized controllers adapted in any suitable manner to provide the desired functionality. For example, the controller 36 may be adapted to provide additional functionality, either complementary or unrelated to the present subject matter. When software is used, any suitable programming, scripting, or other type of language or combinations of languages may be used to implement the teachings contained herein. However, some systems and methods set forth and disclosed herein may also be implemented by hard-wired logic or other circuitry, including, but not limited to, application-specific circuits. Of course, various combinations of computer-executed software and hard-wired logic or other circuitry may be suitable as well.

The signal 38 generated by the controller 36 may be based on any of several parameters being monitored that are reflective of the rotor 10 temperature, thermal gradient across the rotor profile, and/or thermal stresses across the rotor 10. For example, the signal 38 may reflect or be based on a temperature of the rotor 10 that indicates that the temperature profile across the rotor 10 has reached equilibrium. Similarly, the signal 38 may reflect or be based on the temperature of the compressed working fluid exiting the compressor or the combustion gases flowing through the turbine that indicates the maximum outer temperature of the rotor 10. As another example, the signal 38 may reflect or be based on a time interval determined through calculations or testing to be a sufficient time for the rotor 10 to reach equilibrium.

During operation, the fixed orifice 40 may be in the first or open position during start up of the gas turbine to divert a portion of a process fluid, such as the working fluid flowing through the compressor, through the inlet port 24. The diverted fluid would then flow through the fluid passages in the rotor 10, exiting through the outlet port 26 and returning to the flow of compressed working fluid through the compressor or the combustion gases in the turbine. As the diverted fluid heats up the rotor 10, the variable orifice 28 will eventually close. For example, if thermally actuated, the increased temperature will cause the variable orifice 28 to reposition to the second or closed position to reduce or prevent the fluid flow through the fluid passages. Alternately, or in addition, the controller 36 may generate the signal 38 to the variable orifice 28 to reposition the variable orifice 28 between the first or second positions, as desired. In this manner, utilizing the dual metering of the present disclosure allows for the fixed orifice 40 to control fluid flow until a full load condition and the variable orifice 28, which is located at a separate location, to reduce the

The systems described and illustrated with respect to FIGS. 1-3 may also provide a method for controlling flow through the rotor 10. The method may include diverting a process fluid, for example compressed working fluid from the compressor, and flowing the diverted process fluid through fluid passages in the rotor 10, such fluid passage including first and second orifices that are separate from one another. The method may further include reducing the flow of the diverted process fluid through the fluid passages in the rotor 10 using the first orifice and/or the second orifice, for example based on a predetermined temperature limit or a predetermined time limit. In particular embodiments, the variable orifice 28 or valve may be used to reduce the flow of the diverted process fluid through the passage in the rotor 10, and the controller 36 may generate the signal 38 based on a temperature or time.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other and examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 

What is claimed is:
 1. A system for controlling flow through a rotor comprising: a. an inlet port in the rotor; b. an outlet port in the rotor, wherein the outlet port is in fluid communication with the inlet port; c. a fixed orifice disposed in at least one of the inlet or outlet ports; and d. a variable orifice disposed in at least one of the inlet or outlet ports at separate location from the fixed orifice.
 2. The system as in claim 1, further comprising a plurality of passages in the rotor between the inlet port in the outlet port.
 3. The system as in claim 1, wherein the fixed orifice, variable orifice, or combinations thereof comprises a valve.
 4. The system as in claim 1, wherein the fixed orifice, variable orifice, or combinations thereof, has a first position and a second position, wherein the first position permits flow through at least one of the inlet or outlet ports, and wherein the second position prevents flow through at least one of the inlet or outlet ports.
 5. The system as in claim 1, further comprising a controller connected to the fixed orifice, variable orifice, or combinations thereof.
 6. The system as in claim 5, wherein the controller generates a signal to the fixed orifice, variable orifice, or combinations thereof, wherein the signal is based on a temperature.
 7. The system as in claim 5, wherein the controller generates a signal to the fixed orifice, variable orifice, or combinations thereof wherein the signal is based on a time.
 8. A system for warming a rotor comprising: a. a fluid passage through the rotor; b. a first valve disposed in the fluid passage to control the flow of a fluid through the fluid passage; and c. a second valve disposed in a different location of the fluid passage from the first valve to control the flow of a fluid through the fluid passage.
 9. The system as in claim 8, wherein the first valve, second valve, or combinations thereof, has a first position and a second position, wherein the first position permits the fluid to flow through the fluid passage, and wherein the second position prevents the fluid from flowing through the passage.
 10. The system as in claim 8, further comprising a controller connected to the first valve, second valve, or combinations thereof.
 11. The system as in claim 10, wherein the controller generates a signal to the first valve, second valve, or combinations thereof, wherein the signal is based on a temperature.
 12. The system as in claim 10, wherein the controller generates a signal to the first valve, second valve, or combinations thereof, wherein the signal is based on a time.
 13. A method for controlling flow through a rotor comprising: a. diverting a process fluid; b. flowing the diverted process fluid through a fluid passage in the rotor, the fluid passage including a first orifice and a second orifice that is separate from the first orifice; and c. reducing the flow of the diverted process fluid through the fluid passage in the rotor by using the first orifice, second orifice, or combinations thereof.
 14. The method as in claim 13, further comprising diverting the process fluid from a compressor.
 15. The method as in claim 13, further comprising reducing the flow of the diverted process fluid through the fluid passage in the rotor based on a predetermined temperature limit.
 16. The method as in claim 13, further comprising reducing the flow of the diverted process fluid through the fluid passage in the rotor based on a predetermined time limit.
 17. The method as in claim 13, wherein the first orifice, second orifice, or combinations thereof comprises a valve.
 18. The method as in claim 17, further comprising generating a signal to the valve, wherein the signal is based on a temperature.
 19. The method as in claim 17, further comprising generating a signal to the valve, wherein the signal is based on a time. 